Various alignment mechanisms for a light exposure apparatus for use in exposing a work have been suggested in conventional. For example, in the case where a work to be exposed is subjected to solder resist, the surface of the work is a very soft and delicate state and thus, is easy to undergo deformation and damage. When a work in such a delicate state, particularly in the case of a work in a thin film form, is transferred to carry out the light exposure, the transferring mechanism is required to be operated without coming any parts of the transferring mechanism in strongly contact with the work. For this reason, a forwarding transferring mechanism in which the rear surface of the work is caused to be in contact with a transferring belt or transferring rollers to be fed is used as a rule. However, as different from the transfer by the use of a handler, such a forwarding transferring mechanism cannot transfer the work at the state of keeping the work at a constant position and thus, the pre-alignment of the work must be carried out to adjust the position of the work until the alignment is carried out.
One example of such a construction is suggested in Japanese Patent Laid-Open No. 6-310393. To be specific, a light exposure apparatus disclosed therein is composed of a plurality of light exposure stages placed at prescribed gaps and means for moving a work, which is placed within the gaps. In this light exposure apparatus, at least one light exposure stage is placed in a movable manner, and the movable stage is moved to close the gaps at the time of carrying out light exposure.
The means for moving the work (including pre-alignment mechanism of the alignment mechanism) is composed of movable pins in X direction and movable pins in Y direction, which carry out pre-alignment of the work, and transferring belt for transferring the work.
According to this patent publication, it is said that by such a construction, since the work can be pre-aligned by positioning pins placed within the light exposure stages, it becomes suitable to carry out the alignment operation.
Another example of the prior art includes a light exposure process as suggested in Japanese Patent Laid-Open Publication No. 10-218353. This process comprises a step for placing a thin plate work on a top portion of a roller conveyer placed at an inlet side to transfer the work toward a light exposure portion; a step for receiving the transferring work by the top portion of a belt conveyer placed on a light exposure portion to transfer the work toward an upper portion of the light exposure table, a step for descending the belt conveyer to arrange the work on the upper surface of the light exposure table, a step for ascending the belt conveyer after the light exposure, to receive the work on the upper portion of the belt conveyer, and further ascending the belt conveyer to an upper portion of the light exposure table; a step for transferring the work thus ascended to place the work on the upper portion of the belt conveyer out of the light exposure portion; and a step for receiving the transferring work on an upper portion of a roller conveyer placed at an outlet side to transfer the work.
The light exposure table described therein possesses a center main table, and right and left side tables, positioned at both side of the main table in the direction parallel to the transferring direction. When the belt conveyer ascends or descends, the right and left side tables are separated from the main table.
Furthermore, after the work is received on the light exposure table, the pre-alignment mechanism, which pre-aligns the work, has sliding members placed on four corners of the work, which push the edge of the work. The sliding members move along the light exposure table to push the edges of the work, whereby the work is pre-aligned to the center portion. In the case where the work is in a thin plate from, air is blown from air-inlet pores placed on the entire surface of the light exposure table to pick up and float the work from the light exposure table in order to carry out the pre-alignment.
However, the alignment mechanisms and the alignment processes associated with the prior arts have the following problems:
(1) In the alignment mechanism having a construction that the gaps formed between the stages are closed by bringing the side stages into contact with the center stage, since positioning pins in X direction and in Y direction for carrying out pre-alignment are placed inside of the gaps, the pre-alignment can only be carried out when the stages are opened. After the pre-alignment is completed, the stages must be moved in order to close the gaps and, thus, there is a possibility that the work is unduly moved.
(2) In the alignment mechanism having a construction that the sliding members on the light exposure table which can be divided and assembled carry out the pre-alignment, when the work to be operated is a thin plate form, the sliding members cannot push the work in some cases. When the work which is floated by the air, blown from the air-inlet pores provided on the light exposure table is pre-aligned, the work sometimes has an adverse affect by the dust flown due to the air blown.